All nucleic acid detection systems that rely on amplification of either the target being detected or the signal being generated inherently possess a dynamic range that limits their usefulness. At low concentrations of the target being detected, the signal generated is too low to detect or to low to be scored above background levels, and therefore is below the limit of detection, i.e., outside the dynamic range of the detection system. By contrast, at very high levels of the target being generated, the components of the detection system are exhausted such that the signal is said to be saturated, i.e. addition of still more target results in no increase in signal. In these cases, the quantity of target is said to be above the limit of detection, i.e. outside the dynamic range of the detection system.
In the real-world case of detection systems being used to detect targets from biological specimens, the range of target present in the sample being detected can be quite large, and is often either below or above the limit of detection of the system in use. Therefore, previous attempts to cover larger ranges of target concentration have required the generation of more than one detection system, to be used separately, that are optimized for a given dynamic range. Because the quantity of target nucleic acid in the specimen is by definition an unknown quantity, this very frequently requires the use of multiple detection systems sequentially to finally use the appropriate detection system that possesses the appropriate dynamic range for the specimen under examination.
As such, a single detection system with a broader dynamic range, if it was available, would significantly reduce costs, decrease labor time, and decrease expenditure of the specimen being examined. Even more, a method of increasing the dynamic range of an existing detection system would greatly aid the field of detection of targets within biological specimens generally.